Sampras wins 66 points either at net or at baseline. He also won 6 points from Courier's double-faults, and according to Slice Serve Ace he had 61 unreturned serves including aces. So in total that leaves him winning 133 points, very close to Slice Serve Ace's total of 135.

Courier has 71 at net or baseline, 6 from Pete's doubles, and 41 unreturned serves: 118 in total, very close to SSA's total of 120.

In any case the ATP has Sampras leading 163-135 in total points, but they've counted the aces and double-faults twice. If those are only counted once then Sampras leads by 135 to 120, in agreement with SSA's numbers.